ULTRASOUND BASED METHOD AND APPARATUS FOR STONE DETECTION AND TO FACILITATE CLEARANCE THEREOF
Described herein are methods and apparatus for detecting stones by ultrasound, in which the ultrasound reflections from a stone are preferentially selected and accentuated relative to the ultrasound reflections from blood or tissue. Also described herein are methods and apparatus for applying pushing ultrasound to in vivo stones or other objects, to facilitate the removal of such in vivo objects.
This application claims priority from U.S. Provisional patent application 61/326,904 filed Apr. 22, 2010, and from U.S. Provisional patent application 61/474,002 filed Apr. 11, 2011, which are incorporated herein by reference in their entireties.GOVERNMENT RIGHTS
This invention was made with government support under grant numbers DK43881 and DK086371 awarded by National Institutes of Health (NIH) and grant number SMST01601 awarded by National Space Biomedical Research Institute (NSBRI) through NASA NCC 9-58. The government has certain rights in the invention.BACKGROUND
Residual stone fragments such as kidney stones often remain after current methods for stone treatment, such as extracorporeal shockwave lithotripsy, ureteroscopic lithotripsy, and percutaneous nephrolithotomy. In some cases such fragments remain in the lower pole of the kidney. New stones may grow from these fragments, and such fragments have been reported to contribute to a 50% recurrence of kidney stones within 5 years. Thus, improved methods for detecting stones and for facilitating stone clearance from the body are needed.SUMMARY
It is thus one object of the invention to provide an ultrasound detection method and system for stones in a mammal in which ultrasound reflections from stones are selected and displayed preferentially relative to ultrasound reflections from blood or other tissue.
It is another object of the invention to provide an ultrasound detection method and system for stones in a mammal in which ultrasound reflections from stones are selected and displayed preferentially relative to ultrasound reflections from blood or other tissue, wherein the applied ultrasound used for stone detection is B-mode ultrasound.
It is another object of the invention to provide an ultrasound detection method and system for stones in a mammal in which ultrasound reflections from stones are selected and displayed preferentially relative to ultrasound reflections from blood or other tissue, wherein the applied ultrasound used for stone detection is Doppler ultrasound.
It is another object of the invention to provide an ultrasound detection method and system for stones in a mammal in which ultrasound reflections from stones are selected and displayed preferentially relative to ultrasound reflections from blood or other tissue, wherein the applied ultrasound used for stone detection is Doppler ultrasound, and the preferentially selected reflections are those associated with the Doppler ultrasound twinkling artifact.
It another object of the present invention to apply an ultrasonic pushing force to an in vivo stone in a mammal to facilitate clearance.
It is another object of the present invention to apply an ultrasonic pushing force to a stone to facilitate clearance while using detection of the stone.
It is another object of the present invention to apply an ultrasonic pushing force to a stone to facilitate clearance while using ultrasonic detection of the stone.
In accordance with one aspect of the present invention, ultrasound is used to apply a pushing force to a stone in vivo to facilitate clearance, without causing undue damage to the surrounding tissue. The applied pushing ultrasound can be of lower pressure amplitude than ultrasound used in shock wave lithotripsy (“swl”). It also can have a higher duty cycle to create a sustained force that can reposition a stone.
In another aspect of the present invention, the pushing ultrasound is applied in conjunction with detection ultrasound, to allow for detection of the stone such as by visualization on an ultrasound display monitor, or by aural detection. In one embodiment, the detection ultrasound may be a variant of B-mode ultrasound; in another embodiment the detection ultrasound may be a variant of Doppler ultrasound. In a preferred embodiment of the invention, the ultrasound reflections from the stones are selected and displayed preferentially relative to ultrasound reflections from blood and tissue. Where Doppler ultrasound is used, in one embodiment of the invention the twinkling artifact can be used to facilitate detection of the stone. In one aspect of the invention, such detection ultrasound is used to locate a stone prior to the application of the pushing ultrasound. In another aspect of the invention, the detection ultrasound is used in real time to monitor the movement of the stone during the application of the pushing ultrasound.
In one embodiment of any aspect of the present invention, the pushing ultrasound is applied as a focused beam directed along a propagation axis directed to one or more stones or fragments. In another embodiment of any aspect of the invention the pushing ultrasound is applied in an unfocused or weakly focused mode to a general region of anatomy where stones are likely to occur. For example, such unfocused or weakly focused ultrasound energy could be applied generally to a region of a kidney such as the lower pole region to stir up any fragments that might be located therein, thereby facilitating clearance.
In one embodiment of the invention the methods and systems are used to facilitate the removal of stones, such as stones ranging from about 1 to about 10 mm in diameter. In another embodiment, the in vivo stone is fragmented before applying the pushing ultrasound. Such fragmenting can be carried out by any suitable technique, including but not limited to extracorporeal shockwave lithotripsy, ureteroscopic lithotripsy, and percutaneous nephrolithotomy. In another embodiment of any aspect of the invention, the in vivo stone is fragmented after applying the pushing ultrasound, wherein the in vivo stone can be first pushed toward an exit, so that once fragmented, the fragments are more likely to be easily cleared. In another embodiment of the invention, pushing ultrasound is used to induce displacement of stones that may be larger than 10 mm in diameter. For example, displacement of larger stones at the entrance to the ureteropelvic junction (UPJ) would have considerable clinical benefit in relieving pain.
In an exemplary embodiment of the invention for facilitating removal of in vivo stones, detection ultrasound is used to locate the in vivo stone, and pushing ultrasound is used to cause the located in vivo stone to move toward an exit, which exit can be either naturally occurring or provided surgically.
In a further embodiment, the step of using pushing ultrasound to cause the in vivo stone to move is implemented using a quantity of pushing ultrasound sufficient to cause the in vivo stone to move at a rate of at least about one centimeter per second.
In another embodiment, the pushing ultrasound has a pulse duration of about one hundred times that of the detection ultrasound.
In another aspect of the invention the amount of pushing ultrasound used is calculated based on a numerical simulation program, such that ultrasound exposures can be determined for each unique stone and anatomical situation. In such calculations the radiation force on the stone is found using elasticity equations based on the predicted in situ parameters of ultrasound field and expected mechanical properties of the stone, such as density, shear and compressional moduli.
In a further aspect, the present invention provides non-transitory computer readable storage media, for automatically carrying out the methods of the invention on a device, such as an ultrasound device or system according to the invention.
In a further aspect, the system of the present invention displays the stone as it is pushed in real time and tracks the stone motion, continually refocusing the pushing force on the moving stone.
This Summary has been provided to introduce a few concepts in a simplified form that are further described in detail below in the Detailed Description of the Invention. However, this Summary is not intended to limit key or essential features of the claimed subject matter.
Various aspects and attendant advantages of one or more exemplary embodiments and modifications thereto will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
Exemplary embodiments are illustrated in referenced Figures of the drawings. It is intended that the embodiments and Figures disclosed herein are to be considered illustrative rather than restrictive. No limitation on the scope of the technology and of the claims that follow is to be imputed to the examples shown in the drawings and discussed herein. Further, it should be understood that any feature of one embodiment or aspect disclosed herein can be combined with one or more features of any other embodiment or aspect that is disclosed, unless otherwise indicated.
The following additional definitions shall apply in this application:
“Stone”—any piece of calculus material such as may be found, for example, in an organ, duct or vessel of a mammal, and including stones, stone fragments, and stone dust that may result from the application of shock waves or other therapeutic procedures; and equivalent embedded objects for which movement or displacement is desired.
Pressure amplitude—the maximum displacement of the acoustic pressure from ambient.
Duty cycle (also referred to as duty factor)—pulse duration divided by pulse repetition frequency times 100%.
Power—Energy per time, for both electric and acoustic power. Electric power excites the transducer element as a source; acoustic power is in the acoustic wave generated by the transducer element.
Intensity—power transmitted through a cross-sectional area. Cross sectional area can be determined as the beamwidth of the acoustic beam; or as applied to a stone cross sectional area can be the cross section of the stone.
Pulse—an acoustic wave of a certain duration. A single pulse encompasses one or several cycles of pressure oscillation at the center frequency. The excitation of one or more elements in the transducer generates a pulse. Pulses in B-mode tend to be 1-2 cycles and pulses in Doppler tend to be 3-7 cycles. The pulse created by a shock wave lithotripter tends to be 1 cycle.
Doppler Ultrasound—a mode or several modes of ultrasound imaging used to detect blood flow.
B-mode ultrasound—a mode of ultrasound used to create an image of anatomical structures.
Ultrasound waves can be characterized by any one or more of the following intensity parameters:
Temporal peak, ITP, is the highest instantaneous intensity in the beam.
Temporal average, ITA, is the time averaged intensity over the pulse repetition period.
Pulse average, IPA, is the average intensity of the pulse.
Spatial peak, ISP, is the highest intensity spatially in the beam.
Spatial average, ISA, is the average intensity over the beam area.
Spatial average-temporal average intensity, ISATA, is the acoustic power contained in the beam in watts averaged over at least one pulse repetition period, and divided by the beam area.
Spatial average-pulse average intensity, ISAPA=ISATA/duty cycle, where IPA=ITA/duty cycle.
Spatial peak-temporal average intensity, ISPTA=ISATA(ISP/ISA.
Spatial peak-pulse average intensity, ISPPA=ISATA(ISP/ISA)duty cycle.Pushing Ultrasound
Acoustic radiation force results from the transfer of acoustic wave momentum to an absorbing or reflecting object. In the context of the present invention, acoustic radiation of selected pressure amplitude, duration, frequency, and duty cycle is applied to a stone which absorbs the momentum to facilitate non-invasive repositioning of the stone, to allow removal, passage, or further treatment. Such acoustic radiation is referred to herein as pushing ultrasound.
The pushing ultrasound of the system of the present invention will operate at ISPTA>3 W/cm2 in situ. In one preferred embodiment, the pushing ultrasound of the present invention has a time averaged spatial peak intensity of ISPTA>4 W/cm2. A higher pressure can allow for a shorter pulse time or a longer time between pulses. In some embodiments of the invention, the longer time between pulses can be used to real-time imaging between pushing pulses. This is in comparison to diagnostic ultrasound approved for use in the U.S. which must operate at ISPTA<720 mW/cm2 (and MI<1.9) and ISPPA<190 W/cm2, and shock wave lithotripsy and physical therapy ultrasound which operate at ISPTA<3 W/cm2.
Further in accordance with the present invention, pushing ultrasound waves have pressure amplitudes in the range of between about 5 MPa and about 30 MPa, preferably between about 10 MPa and 20 MPa, and most preferably between about 13 MPa and 18 MPa. As is known in the art, detection ultrasound waves generally have a pressure amplitude in the range of about 5 MPa or less, while, ultrasound waves used in shock wave lithotripsy (“swl”) as approved for use in the United States have amplitudes of at least about 30 MPa as measured in water. The high pressures of lithotripsy are necessary to break the stones
The pushing ultrasound waves used in the present invention also are distinguished from other ultrasound waves by the number of cycles per pulse, and by the duty cycle. B-mode ultrasound for detection and shock wave ultrasound for lithotripsy each use a single pulse per cycle; while pushing ultrasound waves used in the present invention use more than one pulse per cycle, typically more than about 5-10 pulses per cycle. Pushing ultrasound waves for use in the present invention can have a duty cycle of greater than 1%. For example, in one embodiment the pushing ultrasound waves pulse for 100 microseconds every three milliseconds. By comparison, lithotripsic ultrasound may run, for example, for a 5 microsecond pulse, with a 250 millisecond duration between pulses, for a duty cycle of <1%.
In a preferred embodiment of the invention, the pushing ultrasound will have a pulse duration of about 100 μs; a center frequency of about 2.3 MHz, a pressure amplitude of about 15 MPa in situ; with bursts repeated every 3 ms, and the total duration of each push sequence being about 1 s. In one embodiment of the invention, imaging pulses can be interleaved within the pushing pulses for real time imaging
The pushing ultrasound facilitates movement of a stone; in one embodiment such movement can be toward an exit location. The exit can be a natural exit of a duct, vessel, or organ, or created surgically. The pushing ultrasound can be more focused when directed to a particular stone, or either weakly focused or unfocused if directed toward a general region of the body such as a kidney pole. For example, a kidney pole area may be suspected of containing very small stone fragments or stone dust which may be difficult to image. Such weakly focused or unfocused pushing ultrasound can be used to stir up the small fragments or dust and facilitate their removal from the pole of the kidney, without the risk of tissue injury that might be caused by shock wave lithotripsy.
In some aspects of the invention, an imaging system can be used to locate the stones for the application of pushing ultrasound. In one embodiment of the invention, such imaging can be accomplished by known imaging techniques such as fluoroscopy. In other embodiments of the invention, such imaging can be accomplished by the application of any of various modes of detection ultrasound, as discussed in greater detail below.Detection Ultrasound
As noted above, in one aspect the inventive system and method disclosed herein employ detection ultrasound to locate stones within an organ, duct, or vessel such as the kidney, wherein the ultrasound waves reflected from a stone are preferentially selected and displayed relative to ultrasound waves reflected off blood or tissue. The detection ultrasound used in connection with the present invention can be based on B-mode ultrasound or Doppler ultrasound, or both.
Doppler ultrasound is a form of ultrasound that can detect and measure blood flow. There are several types of Doppler ultrasound. Color Doppler is a technique that estimates the average velocity of flow within a vessel by color coding the information. The direction of blood flow is assigned the color red or blue, indicating flow toward or away from the ultrasound transducer. Color Doppler can overlay color on a B-mode image. Pulsed Doppler allows a sampling volume or “gate” to be positioned in a vessel visualized on the gray-scale image, and displays a graph of the full range of blood velocities within the gate versus time. The amplitude of the signal is approximately proportional to the number of red blood cells and is indicated, not in color, but simply as a shade of gray. Power Doppler depicts the amplitude, or power, of Doppler signals rather than the velocity. This allows detection of a larger range of velocities and thus better visualization of small vessels, but at the expense of directional and velocity information.
B-mode ultrasound is based on two-dimensional diagnostic ultrasound presentation of echo-producing interfaces in a single plane. B-mode ultrasound is based on brightness modulation, in which bright dots on a screen represent echoes, and the intensity of the brightness indicates the strength of the echo. As is known in the art, the Doppler ultrasound can be overlaid on an image created by B-mode ultrasound, such as to show blood vessels which may appear as red or blue on the ultrasound display.
Standard Doppler detection such as for detecting blood flow is based on small signals that change over time, that are coherent, and have a pattern. At some point in the Doppler image processing, the signals from blood encompass a relatively narrow band of higher frequency and lower amplitude, while ultrasound reflections from tissue such as vessel walls and organ tissue encompass a relatively narrow band of lower frequency and higher amplitude. When using Doppler ultrasound to detect motion of blood, it is known in the art to use an optional “wall filter” which electronically filters from the reflected ultrasound signal the lower frequency, higher amplitude waves reflecting from the vessel walls. When using Doppler ultrasound to evaluate blood flow, it known in the art to autocorrelate data from an ensemble of Doppler pulses, frames, or volumes, in which patterns of coherent data with relatively small changes from pulse to pulse are retained and converted into an image signal, while pulse data that is not part of the coherent pattern is deleted from the signal as unwanted “noise.”
Stones are strong scatterers and therefore reflect strong signals. A signal reflected from stone can change on the next pulse more than a similarly strong signal reflected from tissue. While the cause of the difference in ultrasound reflective properties is not completely understood, it is believed that this difference may be caused by the abruptness of the transition from soft tissue to hard stone, by motion of the stone, or by internal waves in the stone not present in softer tissue. Rather than deleting these signals as unwanted electronic noise as in ultrasound systems of the prior art, in the method and system of the present invention the reflected ultrasound signals are processed such that these strong signals are preferentially retained relative to the narrow bands of coherent signals reflected from blood and tissue, and the retained signals are converted into an image on a display. Thus in contrast to the prior art, the present invention detects stones as strong signals that change over time, with significant change in amplitude that randomly appears in some frames but not others. In some embodiments of the invention these acoustic differences can be exacerbated by nonlinear responses of the front end electronics of the imager.
This feature of the invention in which reflections from stones are preferentially selected and retained in an image display relative to reflections from blood or tissue can be used both with B-mode detection ultrasound and with Doppler detection ultrasound. Where the applied detection ultrasound is Doppler ultrasound, the strong signals that are preferentially selected and displayed as an image can be those reflected waves related to the “twinkling” artifact of ultrasound in which the object being scanned appears brighter or with different colors on the image display monitor.
In those embodiments of the invention in which the pushing ultrasound is used in conjunction with Doppler detection ultrasound, then it is a feature of one embodiment of the present invention that this twinkling artifact can be used to enhance visualization of the stone during the application of pushing ultrasound, thereby allowing for greater control and accuracy in directing the pushing ultrasound toward the stone to be moved. In one embodiment of the invention, an ultrasound system recognizes the twinkling artifact on an ultrasound display and redirects subsequent pulses of pushing ultrasound waves to more efficiently facilitate motion of the stone in a desired direction.
In a further aspect, the present invention provides non-transitory computer readable storage media, for automatically carrying out the methods of the invention on a device, such as an ultrasound device or system according to the invention. As used herein the term “computer readable medium” includes magnetic disks, optical disks, organic memory, and any other volatile (e.g., Random Access Memory (“RAM”)) or non-volatile (e.g., Read-Only Memory (“ROM”)) mass storage system readable by a Central Processing Unit (“CPU”). The computer readable medium includes cooperating or interconnected computer readable medium, which exist exclusively on the processing system or be distributed among multiple interconnected processing systems that may be local or remote to the processing system.
Unless the context clearly dictates otherwise, embodiments in one aspect of the invention may be used in other aspects of the invention, and can be combined with each other.
Probes capable of producing and receiving both detection ultrasound and pushing ultrasound and suitable for use in the present invention include the C4-2 and P4-2 HDI scanheads commercially available from Philips/ATL, although the scope of the invention is not so limited.
While many different acoustic transducers are suitable for pushing ultrasound applications, many ultrasound transducers exhibit a generally conical-shaped beam 26. When probe 10 is positioned so that beam 26 passes through the kidney, acoustic pressure moves a kidney stone from a first position 30a to a second position 30b, closer to an exit 32 which can be either naturally present or artificially introduced such as by surgery. By properly positioning probe 10, the user can control the direction the kidney stone will move. It should be understood that in the context of an artificial exit, the concepts disclosed herein can be used to reposition stones closer to artificially placed tubes/catheters during surgery, such that the method and system disclosed herein can be used intra-operatively.
Acoustic transducer 14 can have a fixed focal length, or a variable focal length. Variable focal length transducers are generally more useful. In applications where a fixed focal length acoustic transducer is used for application of pushing ultrasound, acoustic coupling 16 can be used to control the position of focal region of beam 26 relative to the patient. If a relatively thicker acoustic coupling 16 is employed, the focal region will be disposed closer to dermal layer 20, while if a relatively thinner acoustic coupling 16 is employed, the focal region will penetrate further below the dermal layer and deeper into the subcutaneous target. Thus, the thickness of acoustic coupling 16 can be used to control the position of the focal region relative to a patient's tissue. The transducer may also be a linear, curvilinear, or phased array and be able to steer the beam to push the stone off the axis of the transducer.
In one aspect of the invention the user can interact with user interface 48 to choose an area on the display on which the pushing ultrasound is to be focused. Thus the user can guide the repeated application of pushing ultrasound in real time to urge the stone toward an exit. In one aspect of the invention, the ultrasound system detects the motion of the stone and then sends a new pushing pulse to the new location, to continuously follow the stone on its movement toward an exit. User interface 48 can include a mouse or touch screen as are known in the computer and medical technology arts.
If desired, a separate processing and control component can be employed for each of detection ultrasound component 42 and pushing ultrasound component 44. Displays are sometimes incorporated into conventional detection ultrasound components, and if desired such a display can be used in place of display 50. User interface 48 is employed at least to control the pushing ultrasound component 44, enabling the operator to energize that component as required to achieve the desired movement of the in vivo object. With respect to the operation of pushing ultrasound component 42, if desired, control and processing component 46 can override a command to trigger the pushing ultrasound component if the control and processing component 46 determines that delivery of additional pushing ultrasound could undesirably damage tissue, such as may occur due to thermal or mechanical effects). The processing and control component can be implemented using a custom circuit (i.e., a hardware implementation, such as an application specific integrated circuit) or a processor executing machine instructions stored in a memory (i.e., a software implementation, where the software is executed by a computing device, such as a desktop or laptop computer). Such processing and control components are known to those of ordinary skill in the art.
Thus, in optional block 54, the in vivo object that has been moved closer to an exit is fragmented to facilitate its removal. Any of the known fragmentation techniques can be employed.Example 1
In an empirical study to test the concepts disclosed herein, a pushing ultrasound device was used to move a kidney stone fragment, with the goal of facilitating passage. In one study, natural and artificial stones about 1-8 mm in length were surgically placed in the urine space in pig kidneys. A new system was assembled and programmed to both image stones and push stones. The system had the general design of
In the empirical studies, a research ultrasound device designed for other medical therapies was used, which combines a commercial ultrasound imaging system with a research pushing ultrasound therapy system. The imaging probe is placed within, looking down the axis of, the therapy probe. In the empirical study, longer bursts of higher amplitude focused ultrasound were applied than are generally employed in diagnostic ultrasound (30-ms, 10-MPa bursts repeated at 10 Hz). The force applied to stone fragments and motion of the fluid around the stone caused stone motion. Motion of natural and artificial stones was observed visually in a kidney phantom of transparent tissue mimicking gel surrounding a water-filled space, and with diagnostic ultrasound and fluoroscopy in live and excised pig kidneys.
Stone velocities were on the order of 1 cm/s and stones quickly moved out of the ultrasound focus. Operators could generally control the direction of stone movement.
In the empirical study, a sonographer using Doppler ultrasound and what is known as “twinkling artifact” visualized stones as small as 1 mm in the kidney of a porcine animal model. When pushing ultrasound was applied, these stones were seen on the real-time ultrasound display to jump up at ˜1 cm/s. While in some embodiments pushing ultrasound exposure might result in thermal damage to tissue, no such damage was noted in the empirical study. The empirical study indicated that pushing ultrasound can be used to move stones within a collecting system in order to optimize rates of stone clearance.
It should be noted that while the present novel approach of moving kidney stones (or fragments thereof) using focused ultrasound represents an exemplary embodiment, the concepts disclosed herein can also be used to move other embedded objects, including, but not limited to, stones, fragments and dust located in any of the gall bladder, the salivary tract, and the biliary tract of a human or other mammal.
The following Figures illustrate various modes of detection of stones in accordance with the invention, in which like reference numerals indicate like components. These various modes of detection can be used either alone or in combination with each other and a voting algorithm or with the use of pushing ultrasound to facilitate stone clearance, as discussed above.
In the prior art methods of processing Doppler data, the data are processed to eliminate signals having higher amplitudes, large discontinuities, outliers, and broad band twinkling effects, so that blood and tissue are more readily seen. In each of the following embodiments of the invention, the opposite approach is used, i.e., those signals that are generally discarded in prior art Doppler ultrasound systems are not only retained in the present invention but are accentuated relative to the signals reflected from blood and tissue, to more accurately identify the stones that generate such signals. Each of the embodiments of
The selected values are normalized within the region of interest at step 120; these values are then merged with a B-mode image and displayed at display means 88.
Another aspect of the invention relates to a method for determining the output voltage and threshold level. In considering the distribution of the calculated twinklepower, as the output voltage for the system increases, the distribution of the non stone pixels shifts lower, while the stone pixels remain at the high end of the range. The threshold for display can be set at the high end of the non-stone distribution, but below the stone threshold. This method works because as the output voltage is increased, the tissue signal-to-noise ratio increases and is better filtered by the wall filter, while the effect that causes the stone to twinkle remains.
In one embodiment of one aspect of the invention, any one or more of image processing techniques such as 2D cross-correlation, phase correlation, and feature-edge detection are used to overlay color on the stone in the real-time, B-mode images and to assign a color to indicate the confidence in the identification of the stone.
In another embodiment the system can detect a moving stone, re-target the pushing ultrasound, and apply a new focused push pulse at that location.
It will be recognized by those skilled in the art that any combination of detection algorithms can be combined using a decision matrix to optimize the location of the stone. Also variations of the above methods will be recognized by those skilled in the art. For example, in any of the illustrated embodiments, the beam forming at 84 could be analog beam forming that would then occur prior to digitization. Beam forming also could occur within the ensemble collection loop. Similarly, in each of the foregoing embodiments the system makes a threshold determination as to which information to display at each pixel of display means 88, unless a multi-dimensional color map or semi-transparent layers are used. In the embodiments illustrated herein, the threshold determination is based on the B-mode power and the noise power. Those skilled in the art will recognize that such a threshold determination also could be made on the basis of traditional Doppler power, velocity, variance, higher order moments, or other information that can be obtained from the autoregression model.
It also will be appreciated that any of the detection methods of the present invention as illustrated in
The system described in Example 1 above also was used to perform all the same experiments described in Example 2. The system was operated with the following parameters:
Detection of the fragment was achieved using the imaging described above, B-mode ultrasound, and the twinkling artifact produced by the stones/fragments in Doppler mode ultrasound. In this empirical study, the same elements in the transducer were used for both imaging and pushing. Ultrasound and fluoroscopy showed the stones moving in real-time under the influence of the pushing ultrasound. Stones moved on the order of 1 cm/s away from the source, and several stones moved several centimeters down the ureter. It appeared that such movement was only induced when the stones/fragments were directly in the path of the focal beam, indicating that radiation pressure, as opposed to streaming, caused the motion. While ultrasound imaging and fluoroscopy were used independently in this study to track the initial position and motion of the stone/fragments being moved by the pushing ultrasound, other imaging modalities could be employed. Such imaging modalities include, without limitation, fluoroscopy, computed tomography (CT), low-dose stone protocol CT, B-mode ultrasound, magnetic resonance imaging (MRI), and Doppler ultrasound. When Doppler ultrasound is used the twinkling artifact may make the stones appear brightly colored in the image display. The methods and systems disclosed herein can be adapted to use the twinkling artifact to facilitate visualization of the stones for diagnosis and treatment.Example 2
The system used in the Examples is shown in
All animal studies were acute, and animal research procedures were approved by the University of Washington IACUC. Twelve common domestic female pigs (age 5 months and 50-60 kg) underwent induction of general anesthesia, had their flank regions shaved and depilated, and were secured to the operation room table. In six pigs, artificial stones (radio-opaque glass/metal beads 3 and 5 mm in diameter) and human urinary stones (cystine, calcium oxalate monohydrate, or calcium hydrogen phosphate dihydrate, 1-8 mm) were endoscopically placed into the lower pole using retrograde ureteroscopy, retrograde percutaneous nephrolithomy or open surgical access and canalization of the ureter. A retrograde pyelogram was performed to outline the porcine collecting system. Prior the treatment with focused ultrasound, stone position was visually confirmed endoscopically and fluoroscopically. Most stones were placed in the lower pole but many were placed in upper pole calyces.
Both kidneys were accesses through open surgery in the other six anesthetized pigs. A longer coupling cone was added the array to place the focus 0.5-1 cm beyond the end of the cone. The abdomen was filled with saline to ensure coupling, and the cone was placed in direct contact with the kidney. Five regions on each kidney were targeted, and the surface location marked with ink. Control regions of the kidney received no ultrasound exposure. Other regions received two minute total exposure at 50% duty cycle at time averaged intensities 325 and 1900 W/cm2. The pigs were sacrificed, and the kidneys were harvested. Both kidneys were freshly sectioned for gross examination, and samples embedded for histological analysis. Microscopic examination was performed using serial sections stained with hematoxylin and eosin (H&E) and nicotinamide adenine dinucleotide-diaphorase (NADH-d). Any signs of thermal or mechanical injury to the renal parenchyma were assessed by observers blinded to the exposure conditions.
Most of the effort was visualizing the stone at an appropriate angle to push it into a fluid space toward the UPJ. Angles of focus that were parallel to the axis of the infundibulum resulted in larger displacement of the stone. Stone motion was not observed at all angles of focused ultrasound delivery, but often if stones were pushed toward a tissue interface the stone ricocheted in a direction along the interface. Larger fluid spaces made propulsion easier. Stones were repositioned at all acoustic intensities used: previous in vitro experiments were not successful with lower intensities. It was not observed that a stone was suddenly made to move simply by increasing the power or that stones moved faster with more power. We concluded that the difficulty in moving these stones was primarily due to alignment of the narrow focus on the stone at an appropriate angle.
Although the concepts disclosed herein have been described in connection with the preferred form of practicing them and modifications thereto, those of ordinary skill in the art will understand that many other modifications can be made thereto. Accordingly, it is not intended that the scope of these concepts in any way be limited by the above description.
1. A method for applying an in vivo force to a stone in a body, the method comprising applying pushing ultrasound to the stone in vivo, said pushing ultrasound having an ISPTA>3 W/cm2.
2. The method of claim 1 wherein said pushing ultrasound has ISPTA>4 W/cm2.
3. The method of claim 1 wherein said pushing ultrasound has a pressure amplitude in the range of about 5 MPa to about 30 MPa.
4. The method of claim 3 wherein said pushing ultrasound has a pressure amplitude in the range of about 10 MPa to about 20 MPa.
5. The method of claim 4 wherein said pushing ultrasound has a pressure amplitude in the range of about 13 MPa to about 18 MPa.
6. The method of claim 1 wherein said pushing ultrasound operates at a range of about 5-10 pulses per cycle.
7. The method of claim 6 wherein said pushing ultrasound pulses have a duration of about 100 μs or greater.
8. The method of claim 1 wherein a frequency of said pushing ultrasound is in the range of about 0.25-5 MHz.
9. The method of claim 8 wherein said frequency of said pushing ultrasound is in the range of about 1-4 MHz.
10. The method of claim 9 wherein said frequency of said pushing ultrasound is in the range of about 1-3 MHz.
11. The method of claim 1 wherein the duty cycle of the pushing ultrasound pulses is greater than 1% over a period of about 1 s.
12. The method of claim 1 wherein the spatial peak pulse average intensity of the pushing ultrasound is greater than 190 W/cm2.
13. The method of claim 1 wherein the spatial peak time average intensity of the pushing ultrasound is greater than 720 mW/cm2.
14. The method of claim 1 wherein the intensity and duration of the pushing ultrasound is does not cause thermal coagulation of tissue.
15. The method of claim 1 wherein said pushing ultrasound induces displacement of said stone.
16. The method of claim 15 wherein said displacement is at a rate of about at least one centimeter per second.
17. The method of claim 15 wherein said force is applied to urge said stone toward an exit location.
18. The method of claim 17 wherein said one or more stones are located in a kidney, and said exit location is an exit from the kidney.
19. The method of claim 1 comprising the further step of fragmenting the stone.
20. The method of claim 19, wherein said step of fragmenting the stone is performed before applying the pushing ultrasound.
21. The method of claim 19 wherein said step of fragmenting the stone is performed after applying the pushing ultrasound.
22. The method of claim 1 comprising the further step of detecting said stone before the application of displacing ultrasound.
23. The method of claim 22 wherein said stone is detected through imaging.
24. The method of claim 23 wherein said imaging is accomplished by one or more imaging means selected from the group consisting of fluoroscopy, computer tomography, low-dose stone protocol computer tomography, B-mode ultrasound, Doppler ultrasound, and MRI.
25. The method of claim 24 wherein said imaging is accomplished with Doppler ultrasound.
26. The method of claim 24 wherein said imaging is accomplished with B-mode ultrasound.
27. The method of claim 25 wherein locating the stone comprises use of a twinkling artifact of Doppler ultrasound.
28. The method of claim 24 wherein the imaging comprises real-time imaging.
29. The method of claim 24 wherein said imaging is accomplished with Doppler ultrasound or B-mode wherein the frequency of said imaging ultrasound is in the range of about 1-5 MHz.
30. The method of claim 30 wherein said frequency of said imaging ultrasound is in the range of about 2-4 MHz.
31. The method of claim 30 wherein said frequency of said imaging ultrasound is in the range of about 2-3 MHz.
32. An ultrasound detection method for detecting stones in a mammal in which ultrasound reflections from stones are selected and displayed preferentially relative to ultrasound reflections from blood or other tissue.
33. The ultrasound detection method of claim 32 in which ultrasound reflections from stones are selected and displayed preferentially relative to ultrasound reflections from blood or other tissue, wherein the applied ultrasound used for stone detection is B-mode ultrasound.
34. The method of claim 33 wherein the selected and displayed ultrasound reflections are magnified and displayed with additional color.
35. The method of claim 33 wherein the selection of ultrasound reflections from stones is based on ultrasound shadows generated when ultrasound is reflected from a stone.
36. The method of claim 33 wherein said display is derived from a spatial derivative of the intensity map of said reflected ultrasound.
37. The ultrasound detection method of claim 33 wherein the applied ultrasound used for stone detection is Doppler ultrasound.
38. The ultrasound detection method of claim 34, wherein the applied ultrasound used for stone detection is Doppler ultrasound, and the preferentially selected reflected are those associated with the Doppler ultrasound twinkling artifact.
39. The method of claim 38, wherein one frame with a Doppler ensemble is amplified by 5-10% to facilitate preferential selection of the reflected ultrasound signal to be displayed.
40. The method of claim 38, wherein outliers within a Doppler ensemble are statistically identified to facilitate preferential selection of the reflected ultrasound signal to be displayed.
41. The method of claim 38, wherein a statistical variance analysis is performed on a Doppler ensemble to facilitate preferential selection of the reflected ultrasound signal to be displayed.
42. The method of claim 38, wherein an autoregression analysis is performed on a Doppler ensemble to facilitate preferential selection of the reflected ultrasound signal to be displayed.
43. A system for applying an in vivo force to a stone in a body, the system comprising
- a. a computer processing unit (CPU);
- b. an ultrasound transducer;
- c. a user interface
- wherein each of said ultrasound transducer and user interface are operatively connected through said central processing unit, said ultrasound transducer being operable to apply pushing ultrasound waves to said stone, said pushing ultrasound waves having an ISPTA>3 W/cm2.
44. The system of claim 43 further comprising an imaging apparatus.
45. The system of claim 44 wherein said imaging apparatus uses Doppler ultrasound or B-mode ultrasound.
46. The system of claim 44 wherein said imaging apparatus and said pushing ultrasound apparatus are operable simultaneously to allow the use of real time imaging of said one or more stones during the application of force thereto.
47. The system of claim 45 wherein the frequency of said imaging ultrasound is in the range of about 1-5 MHz.
48. The system of claim 21 wherein said pushing ultrasound apparatus comprises a handle, a transducer mounted on said handle, and an acoustic coupling operatively engaged with said transducer.
49. The system of claim 48 wherein said transducer has a fixed focal length.
50. The transducer of claim 48 wherein said transducer has a variable focal length.
51. The system of claim 45 wherein said Doppler ultrasound produces a twinkling artifact which is used to facilitate locating said stone.
52. The system of claim 43 wherein said transducer applies Doppler ultrasound to an anatomical region, such that said Doppler ultrasound detects a stone and laminar blood flow, and wherein said central processing unit is operable to optimize the image of said stone in twinkling format relative to said laminar blood flow, whereby said stone is more apparent on said image.
53. The system of claim 52 wherein said optimization comprises suppressing detection of said laminar blood flow.
54. The system of claim 52 wherein said image of said stone is enhanced in the display.
55. The system of claim 52 wherein said stone is displayed in color on said image.
56. The system of claim 52 wherein B-mode ultrasound is used to confirm detection of said stone.
57. The system of claim 52 wherein B-mode ultrasound is applied to the stone at a plurality of angles.
58. The system of claim 53 in which a point on the displayed image can be selected to indicate the anatomical site at which to apply focused ultrasound waves to said stone thereby to displacement of said one or more stones.
59. The system of claim 58 in which the movement of said stone is detected, and said system automatically refocuses on the new location and transmits focused ultrasound to said new location.
60. The system of claim 59 in which the steps of detecting a new stone location and automatically refocusing ultrasound waves to said new location is repeated a plurality of times to cause movement of said stone in a desired direction.
Filed: Apr 22, 2011
Publication Date: Oct 27, 2011
Patent Grant number: 9204859
Applicants: of higher education having a principal place of bussiness (Seattle, WA),
Inventors: Michael Bailey (Seattle, WA), John Kucewicz (Seattle, WA), Wei Lu (Seattle, WA), Oleg Sapozhnikov (Seattle, WA), Paul Illian (Seattle, WA), Anup Shah (Seattle, WA), Barbrina Dunmire (Burien, WA), Neil Owen (Seattle, WA), Bryan Cunitz (Seattle, WA), Peter Kaczkowski (Seattle, WA), Marla Paun (Shoreline, WA)
Application Number: 13/092,811
International Classification: A61B 5/055 (20060101); A61B 8/00 (20060101); A61N 7/00 (20060101);